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Pretreatment with the heterocyclic compound EDU (N-[2-(2-oxo-1-imidazolindinyl)ethyl]-N'-phenylurea) has previously been shown to reduce polymorphonuclear leukocyte (PMN) infiltration into the airways of ozone-exposed rats. The present study further examined the effects of 1 and 2 days EDU pretreatment on rat lung inflammatory responses by determining PMN infiltration in response to intratracheal instillation with the chemoattractant formyl-norleucine-leucine-phenylalanine (fNLP). Maximal recovery of PMNs by bronchoalveolar lavage was observed 4 hr after fNLP instillation with no alteration in the numbers of recoverable macrophages and lymphocytes. Although 1-day pretreatment with EDU did not affect PMN recovery from fNLP-instilled rat lungs, 2 days of EDU pretreatment prevented PMN infiltration as indicated by PMN recoveries that were similar to those obtained from saline-instilled lungs. Measurements of lung-marginated and interstitial pools of inflammatory cells using collagenase tissue digestion demonstrated no effect of 2 days EDU pretreatment. Although 2 days EDU pretreatment alone did not alter blood PMN content, lung permeability, and the lavage recoveries of inflammatory cells, blood PMN responses to chemotactic stimuli in vitro were impaired. In addition, EDU was shown to directly inhibit PMN chemotaxis and superoxide anion generation in vitro. These data demonstrated that EDU acts by interfering with PMN activation and migration rather than by decreasing PMN availability. EDU, by modulating the inflammatory response, represents a useful compound for preventing PMN-associated amplification of acute lung injuries.

The ability of the heterocyclic compound EDU (N-[2-(2-oxo-1-imidazolindinyl)-ethyl]-N'-phenylurea) to affect polymorphonuclear leukocyte (PMNL) activation was examined by measuring superoxide anion, hydrogen peroxide and hydroxyl radical release from human PMNLs stimulated by phorbol ester. Results demonstrated that EDU effectively interferes with PMNLs reactive oxygen intermediate production, making it a potentially useful compound to be used to modulate PMNL-associated oxidant damage of inflamed tissues.

The phenylurea compound EDU (N-[2-(2-oxo-1-imidazolindinyl)ethyl]-N'-phenylurea) has been shown to protect plants from the damaging effects of ozone exposure. Models of rat lung injury, based on acute exposure to 2 ppm ozone for 3 hr and on exposure to 0.85 ppm ozone for 2 days, were used to determine whether EDU pretreatment of rats protected lungs from oxidant injury. Rats were pretreated with 100 mg/kg body wt EDU by ip administration for 2 days prior to and on the days of ozone exposure. No adverse toxicological effects of EDU pretreatment were observed. Lung superoxide dismutase (SOD) and catalase (CAT) activities were significantly enhanced from 636 to 882 U/lung and from 599 to 856 U/lung, respectively. One day following acute exposure (2 ppm for 3 hr), an ozone-induced increase of polymorphonuclear leukocytes (PMNs) from 0.01 to 1.18 million cells/lung was decreased to 0.68 million by EDU pretreatment. No alteration occurred in the degree of lung permeability indicated by increased lavage fluid albumin. EDU pretreatment also significantly decreased ozone-induced increases in PMN recovery after 2 days exposure to 0.85 ppm ozone from 5.54 to 2.12 million cells/lung. However, in this second case, EDU pretreatment reduced the observed ozone damage, indicated by a decrease in lavage fluid albumin and by a decrease in the macrophage and lymphocyte infiltration associated with this length of ozone exposure. The observation that EDU-treated cultured pulmonary arterial endothelial cells increased SOD and CAT activities identified a potential lung site of EDU interaction. These data demonstrated that although EDU pretreatment appears not to prevent initial ozone damage, it does reduce the infiltration of PMNs and might therefore prevent amplification of the injury associated with this cell type.

Oxygen free radicals have the potential to mediate cell injury. Defenses against such radicals include the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX). The purposes of this study were (1) to develop an in vitro model using human cells in which to investigate a potential pharmacologic agent as an inducer of these antioxidant enzymes; (2) to investigate the phenylurea derivative N-[2-(2-oxo-1-imidazolindinyl)ethyl]-N-phenylurea (EDU) in this model with paraquat (PQ) serving as the positive control; and (3) to determine if induction of the antioxidant enzymes by EDU occurs in vivo. Human gingival fibroblasts (Gin-1) were used as the target cell in vitro; PQ and EDU, an inducer of SOD and CAT activities in plants, were evaluated as antioxidant enzyme inducers. Total SOD activity in Gin-1 cells increased 2-fold (p less than 0.05) in the presence of 1.0 mM PQ for 18-48 hr compared with untreated controls. Gin-1 cells incubated with 0.25-2.0 mM PQ for 24 hr had significantly increased total SOD (1.5 to 2.0-fold; p less than 0.05). CAT activity increased with 1.0 and 2.0 mM PQ (p less than 0.05). In the presence of PQ, GSH-PX activity decreased (p less than 0.05) in a concentration-dependent manner, indicating inactivation of this enzyme. No toxicity, indicated by lactate dehydrogenase released into the incubation medium, was noted at PQ concentrations below 5.0 mM. In the presence of 0.125-2.0 mM EDU, total SOD activity in Gin-1 cells significantly increased (1.5 to 2.0-fold; p less than 0.05). CAT activity significantly increased in a dose-dependent manner (p less than 0.05), while GSH-PX activity remained constant following exposure to 0.125-2.0 mM EDU. Intraperitoneal administration of EDU to rats twice a day for 2 days at 100 mg/kg induced SOD activity in heart, liver, and lung compared to controls (p less than 0.05). CAT activity increased in the liver 56% and in the lung 36% (p less than 0.05). GSH-PX activity remained constant. Our findings indicate that Gin-1 cells are a useful model in which to study inducers of antioxidant enzymes in vitro and that the phenylurea compound EDU induces SOD and CAT activities both in vitro and in vivo.